Question

MIPS QUESTION

This project will entail reading in a string of 4 characters into a variable (Beware if Endians). You must then take each individual character and load them into separate register ($t0-$t3). They then MUST be placed on the stack and then “popped off” in reverse order The resulting output should print the characters in reverse order.

Some things to note:

1. Remember the Endians.
2. When reading in a string, you must allocate an extra byte (5 instead of 4).
3. FIFO
4. For reading the string, use code 8 in $v0.

Some useful instructions:

lb, sll,sb, lb $t0,1($sp), , sb $t0,1($sp), addi $sp,$sp,1 and ), addi $sp,$sp,4

Answer 1

Screenshot

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Program

#Data declaration part
.data
   input: .asciiz "Enter a 4 letter string: "
   buff: .byte 5
#Program starts here
.text
     #Display prompt
     addi $v0,$0,4
     la $a0,input
     syscall
     #read string
     addi $v0,$0,8
     la $a0,buff
     addi $a1,$0,5
     syscall
     #Call method to reverse
     jal reverse
     #End of the program
     addi $v0,$0,10
     syscall
#Reverse function
reverse:
     #Allocate stack
     addi $sp,$sp,-16
    #store each characters into registers
     lbu $t0,($a0)
     lbu $t1,1($a0)
     lbu $t2,2($a0)
     lbu $t3,3($a0)
     #store each characters into stack
     sb $t0,($sp)
     sb $t1,4($sp)
     sb $t2,8($sp)
     sb $t3,12($sp)
     #For next line
     addi $v0,$0,11
     li $a0,10
     syscall
     #Pop in reverse order
     lbu $a0,12($sp)
    addi $v0,$0,11
     syscall
     lbu $a0,8($sp)
    addi $v0,$0,11
     syscall
     lbu $a0,4($sp)
     addi $v0,$0,11
     syscall
     lbu $a0,0($sp)
     addi $v0,$0,11
     syscall
     #de allocate stack
     addi $sp,$sp,16
     #return
     jr $ra
-----------------------------------------

Output

Enter a 4 letter string: HELL
LLEH
-- program is finished running --